Superior Piezocatalytic Activity of the (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ Crystal Catalyst Induced by Sm₂O₃ Doping: Morphotropic Phase Transition and Defect Engineering

Piezocatalysis has emerged as a promising technology for environmental remediation by harnessing mechanical energy to drive redox reactions. In this study, Sm₂O₃-doped (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT) solid solutions have been synthesized via a facile solid-state reaction to systematically investigate the effects of Sm³⁺ doping on the phase structure, defect chemistry, and piezocatalytic activity. Rietveld refinement, transmission electron microscopy, and Raman spectroscopy all confirm the coexistence of rhombohedral, orthorhombic, and tetragonal phases. The morphotropic phase boundary (MPB) promotes polarization rotation and enhances the piezoelectric response. The thermally stimulated depolarization current (TSDC) measurements reveal that the lowest defect (particularly oxygen vacancy) density is found in the BCZT samples doped with 0.02 wt % Sm₂O₃, which enable the materials to possess exceptional piezocatalytic performance, yielding a high degradation efficiency (96.8%) of rhodamine B within 30 min at a rate constant of 0.1156 min^–1. Carrier separation and migration capabilities have been boosted through electrochemical and band structure analyses. This work indicates that Sm₂O₃ doping introduces local structural heterogeneity and optimizes the defect state for the host materials, providing an effective strategy for designing high-performance eco-friendly piezocatalysts.